Micro array technology has revolutionized the biotechnology industry. Its ability to process large number of biological samples in parallel is unprecedented. The current micro array technologies can be generally categorized into two groups. One group is based on a two-dimensional solid support system, on which all the biological reactions and signal detections are completed (see e.g., “Large-scale identification, mapping and genotyping of single-nucleotide polymorphisms in the human genome” by Wang, D. G., et al., Science, Volume 280: pages 1077-1082 (1998)). The other group utilizes microparticles as reaction platform. One example of such technology is the fluorescent particle technology or three-dimensional micro array (see e.g. “Multiplexed particle-based flow cytometric assays” by Vignali, D A., J. Immunol. Methods, Volume 243, pages 243-255 (2000); “Multiplexed analysis of human cytokines by use of the FlowMetrix system” by Oliver K G, et al., Clinical Chemistry Volume 44, Pages 2057-2060 (1998); and U.S. Pat. Nos. 6,057,107, 5,981,180 and 5,736,330). Limitations have been observed on both types of technologies. Biological reaction conducted on the two-dimensional based technology platform is limited by molecule diffusion. In general, a longer reaction time is required for the two-dimensional reaction platforms. The three-dimensional fluorescence particle technology has problems in the complexity of the technology and limitation on numbers of particle encoding, e.g., only hundreds or thousands of encoding are available. In addition, the detection of two-color fluorescence levels on the microparticles requires sophisticated instrumentation.
WO 00/16893 discloses a system for carrying out parallel bioassays. Microfabricated labels are made to each carry a biochemical test, many different labels are mixed together with an analyte sample. A device that reads the individual labels isolates the results of the individual tests. The microfabricated labels have a surface layer of anodized metal and are produced by anodizing, lithographic patterning and etching steps. Aluminum is the preferred metal.
In modern pharmaceutical industry, a very important approach for developing new drugs is through the screening of combinatorially synthesized compound libraries. Combinatorial chemistry is high-throughput, rapid and “synchronized” method that can synthesize the structurally-similar compounds and derivatives of a lead compound. While previous synthesis methods are primarily based on individual compound synthesis, combinatorial chemistry is capable of synthesizing thousands to tens of thousands compounds in serial and parallel fashions (Dolle, Journal of Combinatorial Chemistry, 2:383-433 (2000)).